<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
    <script src="../react18/react.development.js"></script>
    <script src="../react18/react-dom.development.js"></script>
    <script src="../react18/babel.min.js"></script>
  </head>
  <body>
    <div id="app"></div>
    <script type="text/babel">
      function App() {
        const [count, setCount] = React.useState(0);
        const [username, setUsername] = React.useState("");
        React.useEffect(() => {
          console.log("useEffect调用了");
        });
        React.useEffect(() => {
          console.log("useEffect调用，但只调用初始化");
          setUsername("hello");
        }, []);
        React.useEffect(()=>{
            console.log('useEffect调用依赖于count')
            
        },[count])
        return (
          <div>
            <h1>App:{count}</h1>
            <p>username:{username}</p>
            <button onClick={()=>{
                setCount((x) => x + 1)
            }}>改变</button>
          </div>
        );
      }
      ReactDOM.createRoot(document.getElementById("app")).render(<App />);
    </script>
  </body>
</html>
